Betulin-containing birch bark extracts and their formulation

Abstract

The present disclosure relates to birch bark extracts, methods of producing such extracts, stable pharmaceutical compositions containing such extracts and methods of using of such extracts. The birch bark extracts of the present disclosure contain triterpenes, which are known to improve wound healing.

What is claimed is: 
     
         1 . A solid birch bark extract comprising at least about 70 wt. % betulin and one or more triterpenes selected from the group consisting of betulinic acid, oleanolic acid, erythrodiol, and lupeol. 
     
     
         2 . The solid birch bark extract of  claim 1 , wherein the solid birch extract has an HPLC chromatogram substantially identical to  FIG. 1  when chromatographed according to the following HPLC method: 
       
         
           
                 
                 
                 
                 
                 
               
                     
                 
                   Time 
                     
                     
                   H 3 PO 4   
                   Flow rate 
                 
                   (min) 
                   Acetonitrile 
                   Water 
                   (v/v) 
                   (ml/min) 
                 
                     
                 
                     
                 
                 
                 
                 
                 
                 
               
                   0 
                   30 
                   70 
                   0.1% 
                   0.6 
                 
                   5 
                   30 
                   30 
                   0.1% 
                   0.6 
                 
                   15 
                   98 
                   2 
                   0.1% 
                   0.6 
                 
                   20 
                   98 
                   2 
                   0.1% 
                   0.6 
                 
                   21 
                   30 
                   70 
                   0.1% 
                   0.6 
                 
                   30 
                   30 
                   70 
                   0.1% 
                   0.6 
                 
                     
                 
                   Column: C18, 2.6 μm, 150 × 2.1 mm; detector: 210 and 320 nm; 
                 
             
                
                
                
                
               
               
                
               
            
             
                
                
                
                
                
                
                
                
               
            
           
         
         wherein the betulinic acid has a relative retention time of about 0.75-0.90, the oleanolic acid has a relative retention time of about 0.84-0.97, the betulin has a relative retention time of 1.00, the erythrodiol has a relative retention time of about 1.25-1.40, and the lupeol has a relative retention time of about 3.50-4.15. 
       
     
     
         3 . The solid birch bark extract of  claim 1  or  claim 2 , prepared by a process comprising:
 (a) contacting birch bark with a pharmaceutically acceptable solvent, thereby forming an extraction solution comprising betulin and one or more triterpenes; 
 (b) separating the birch bark from the extraction solution; 
 (c) cooling the extraction solution whereby a portion of the betulin and one or more triterpenes crystallizes from the cooled extraction solution; 
 (d) separating the crystallized betulin and one or more triterpenes from the cooled extraction solution; 
 (e) drying the separated, crystallized betulin and one or more triterpenes to provide the solid birch bark extract; 
 wherein if after drying, about 1 wt. % to about 20 wt. % of the dried solid birch bark extract of step (e) dispersed in refined sunflower oil forms an oleogel. 
 
     
     
         4 . The solid birch bark extract of  claim 3 , wherein one or more of steps (a), (c), and (e) is carried out under the following conditions:
 (i) said contacting of step (a) is carried out at a temperature of about 60° C. to about 130° C.;   (ii) said cooling of step (c) is carried out at a temperature of about −20° C. to about 35° C.;   (iii) said drying of step (e) is carried out at a temperature of about 75° C. to about 95° C. at a pressure of less than about 70 mbar.   
     
     
         5 . The solid birch bark extract of  claim 3 , wherein two or more of steps (a), (c), and (e) are carried out under the following conditions:
 (i) said contacting of step (a) is carried out at a temperature of about 60° C. to about 130° C.;   (ii) said cooling of step (c) is carried out at a temperature of about −20° C. to about 35° C.;   (iii) said drying of step (e) is carried out at a temperature of about 75° C. to about 95° C. at a pressure of less than about 70 mbar.   
     
     
         6 . The solid birch bark extract of  claim 3 , wherein steps (a), (c), and (e) are carried out under the following conditions:
 (i) said contacting of step (a) is carried out at a temperature of about 60° C. to about 130° C.;   (ii) said cooling of step (c) is carried out at a temperature of about −20° C. to about 35° C.;   (iii) said drying of step (e) is carried out at a temperature of about 75° C. to about 95° C. at a pressure of less than about 70 mbar.   
     
     
         7 . The solid birch bark extract of any one of  claims 3 - 6 , wherein the pharmaceutically acceptable solvent is a hydrocarbon or alcohol, or combinations thereof. 
     
     
         8 . The solid birch bark extract of any one of  claims 3 - 7 , wherein the pharmaceutically acceptable solvent is a hydrocarbon selected from the group consisting of n-pentane, n-hexane, or n-heptane. 
     
     
         9 . The solid birch bark extract of  claim 8 , wherein the pharmaceutically acceptable solvent is n-heptane, and said contacting is carried out at a temperature of about 60° C. to about 130° C. for about 8-12 minutes. 
     
     
         10 . The solid birch bark extract of any one of  claims 3 - 9 , wherein in step (c) the cooled extraction solution is supersaturated at least about 2-fold. 
     
     
         11 . The solid birch bark extract of  claim 10 , wherein the cooled extraction solution is supersaturated about 5-fold. 
     
     
         12 . The solid birch bark extract of any of  claims 3 - 11 , wherein the amount of residual extraction solvent is no more than about 0.5 wt. %. 
     
     
         13 . An oleogel comprising about 1 wt. % to about 20 wt. % of particles of the solid birch bark extract of any one of  claims 1 - 12 , having an average particle size of less than about 50 μm, dispersed in about 80 wt. % to about 99 wt. % of one or more nonpolar liquids. 
     
     
         14 . The oleogel of  claim 13 , wherein the dispersed solid birch bark extract particles are the only oleogel forming agent in the oleogel. 
     
     
         15 . The oleogel of  claim 13 , comprising about 10 wt. % of particles of the solid birch bark extract. 
     
     
         16 . The oleogel of  claim 13  or  15 , wherein the nonpolar liquid comprises at least one triglyceride. 
     
     
         17 . The oleogel of  claim 13  or  15 , wherein the nonpolar liquid comprises at least one C7 or greater hydrocarbon. 
     
     
         18 . The oleogel of  claim 16 , wherein the nonpolar liquid comprises one or more vegetable oils. 
     
     
         19 . The oleogel of  claim 18 , wherein the nonpolar liquid comprises sunflower oil. 
     
     
         20 . The oleogel of any one of  claims 13 - 19 , wherein the nonpolar liquid has a peroxide value less than about 10. 
     
     
         21 . The oleogel of  claim 20 , wherein the peroxide value is no more than about 3. 
     
     
         22 . The oleogel of any one of  claims 13 - 21 , wherein the oleogel is substantially free of solid birch bark extract particles having a size greater than about 50 μm. 
     
     
         23 . The oleogel of any one of  claims 13 - 22 , wherein the oleogel is sterile. 
     
     
         24 . The oleogel of  claim 23 , wherein the oleogel is sterilized by ionizing irradiation at doses less than about 20 kGy. 
     
     
         25 . The oleogel of  claim 24 , wherein the oleogel is sterilized by ionizing irradiation at doses ranging from about 11 to about 20 kGy. 
     
     
         26 . The oleogel of any one of  claims 13 - 25 , wherein the segregation of the nonpolar liquid from the oleogel is less than about 10% after centrifuging at 25° C. for 30 min at 2750 g. 
     
     
         27 . The oleogel of any one of  claims 13 - 26 , wherein the viscosity at 200/s of the oleogel ranges from about 0.5 to about 4.0 Pa·s and the thixotropy value of the oleogel ranges from about 200 to about 1200 Pa·s as measured according to the rotating viscometer method described in Ph. Eur. 2.2.10 using a cone-plate viscometer. 
     
     
         28 . The oleogel of any one of  claims 13 - 27 , wherein the consistency of the oleogel ranges from about 300-3000 mN as measured according using a texture analyser. 
     
     
         29 . The oleogel of any one of  claims 13 - 28 , further comprising a disinfectant. 
     
     
         30 . The oleogel of  claim 29 , wherein the disinfectant is selected from the group consisting of ethanol, n-propanol, and isopropanol. 
     
     
         31 . The oleogel of any one of  claims 13 - 28 , further comprising a lipophilic antibiotic. 
     
     
         32 . A sterile wound dressing comprising:
 (a) a pad, and   (b) a therapeutically effective layer comprising the oleogel of any of  claims 13 - 31  disposed on at least one surface of the pad.   
     
     
         33 . The sterile wound dressing of  claim 32 , wherein the pad is an absorbent pad. 
     
     
         34 . A process for preparing the solid birch bark extract of  claim 1  or  claim 2  comprising:
 (a) contacting birch bark with a pharmaceutically acceptable solvent, thereby forming an extraction solution comprising betulin and one or more triterpenes; 
 (b) separating the birch bark from the extraction solution; 
 (c) cooling the extraction solution whereby a portion of the betulin and one or more triterpenes crystallizes from the cooled extraction solution; 
 (d) separating the crystallized betulin and one or more triterpenes from the cooled extraction solution; 
 (e) drying the separated, crystallized betulin and one or more triterpenes to provide the solid birch bark extract; 
 wherein after drying, about 1 wt. % to about 20 wt. % of the dried solid birch bark extract of step (e) dispersed in refined sunflower oil forms an oleogel. 
 
     
     
         35 . The process of  claim 34 , wherein one or more of steps (a), (c), and (e) is carried out under the following conditions:
 (i) said contacting of step (a) is carried out at a temperature of about 60° C. to about 130° C.;   (ii) said cooling of step (c) is carried out at a temperature of about −20° C. to about 35° C.;   (iii) said drying of step (e) is carried out at a temperature of about 75° C. to about 95° C. at a pressure of less than about 70 mbar.   
     
     
         36 . The process of  claim 34 , wherein two or more of steps (a), (c), and (e) are carried out under the following conditions:
 (i) said contacting of step (a) is carried out at a temperature of about 60° C. to about 130° C.;   (ii) said cooling of step (c) is carried out at a temperature of about −20° C. to about 35° C.;   (iii) said drying of step (e) is carried out at a temperature of about 75° C. to about 95° C. at a pressure of less than about 70 mbar.   
     
     
         37 . The process of  claim 34 , wherein steps (a), (c), and (e) are carried out under the following conditions:
 (i) said contacting of step (a) is carried out at a temperature of about 60° C. to about 130° C.;   (ii) said cooling of step (c) is carried out at a temperature of about −20° C. to about 35° C.;   (iii) said drying of step (e) is carried out at a temperature of about 75° C. to about 95° C. at a pressure of less than about 70 mbar.   
     
     
         38 . The process of  claim 34 , wherein the pharmaceutically acceptable solvent is a hydrocarbon selected from the group consisting of n-pentane, n-hexane, or n-heptane. 
     
     
         39 . The process of any one of  claims 34 - 38 , wherein the pharmaceutically acceptable solvent is n-heptane, and said contacting is carried out at a temperature of about 115° C. to about 130° C. for about 8-12 minutes. 
     
     
         40 . The process of any one of  claims 34 - 39 , wherein in step (c) the cooled extraction solution is supersaturated at least about 2-fold. 
     
     
         41 . The process of  claim 40 , wherein the cooled extraction solution is supersaturated about 5-fold. 
     
     
         42 . The process of any of  claims 34 - 41 , wherein the amount of residual extraction solvent is no more than about 0.5 wt. %. 
     
     
         43 . An emulsion comprising the solid birch bark extract of any of  claims 1 - 12 . 
     
     
         44 . An emulsion comprising the oleogel of any of  claims 13 - 31 . 
     
     
         45 . The emulsion of  claim 43  or  44 , wherein said emulsion is a water-in-oil emulsion. 
     
     
         46 . The emulsion of  claim 45 , substantially free of emulsifier. 
     
     
         47 . The emulsion of any one of  claims 43 - 46 , consisting essentially of the solid birch bark extract or oleogel, oil, and water. 
     
     
         48 . The emulsion of any one of  claims 44 - 46 , consisting of the oleogel, oil and water. 
     
     
         49 . The emulsion of any one of  claims 43 - 46 , further comprising a disinfectant. 
     
     
         50 . The emulsion of  claim 49 , wherein the disinfectant is selected from the group consisting of ethanol, n-propanol, and isopropanol. 
     
     
         51 . The emulsion of any one of  claims 43 - 46 , further comprising a lipophilic antibiotic. 
     
     
         52 . A foam comprising the emulsion of any one of  claims 43 - 51 . 
     
     
         53 . The foam of  claim 52 , further comprising a disinfectant. 
     
     
         54 . The foam of  claim 53 , wherein the disinfectant is selected from the group consisting of ethanol, n-propanol, and isopropanol. 
     
     
         55 . The foam of  claim 52 , further comprising a lipophilic antibiotic. 
     
     
         56 . The foam of any of  claims 52 - 55 , wherein the interfacial surface tension of the emulsion is greater than about 4 mN/m. 
     
     
         57 . The foam of any of  claims 52 - 56 , wherein the foam index is greater than about 2. 
     
     
         58 . The foam of  claim 52 , wherein the oleogel consists of about 5 wt. % to about 10 wt. % solid birch bark extract and the emulsion is a water-in-oil emulsion consisting of the oleogel and about 20 wt. % to about 30 wt. % of water. 
     
     
         59 . The foam of  claim 58 , wherein the oleogel consists of about 7 wt. % solid birch bark extract and the amount of water in the emulsion is about 25 wt. %. 
     
     
         60 . The foam of any of  claims 52 - 56 , further comprising an emulsifier selected from the group consisting of phosphatidyl choline, polyglyceryl-3-methyl glucose distearate, and combinations thereof. 
     
     
         61 . A pressurized container filled with a mixture comprising the emulsion of any one of  claims 43 - 51  and a pharmaceutically acceptable propellant, whereby the emulsion forms a foam upon decanting at least a portion of the mixture from the container. 
     
     
         62 . A method of treating a wound in a patient comprising topically administering the oleogel of any one of  claims 13 - 31  to at least a portion of the wound. 
     
     
         63 . The oleogel of any one of  claims 13 - 31 , for use in a method of treating a wound. 
     
     
         64 . The method or oleogel for use of  claim 63 , wherein the wound is selected from the group consisting of a burns, surgical skin lesions, superficial injuries, chronic wounds, pressure ulcers, diabetic foot ulcers, chronic venous ulcers, artery insufficiency ulcers, wounds from aesthetic skin treatments, wounds from ablative laser skin treatments, wounds from chemical peels, wounds from dermabrasion, wounds resulting from adverse drug reactions, wounds resulting from toxic epidermal necrolysis, wounds resulting from Lyell syndrome, wounds resulting from Stevens-Johnson syndrome, and wounds resulting from radiation dermatitis. 
     
     
         65 . A method of treating a wound in a patient comprising topically administering the emulsion of any one of  claims 43 - 51  to at least a portion of the wound. 
     
     
         66 . The emulsion of any one of  claims 43 - 51 , for use in a method of treating a wound. 
     
     
         67 . The method or emulsion for use of  claim 66 , wherein the wound is selected from the group consisting of burns, surgical skin lesions, superficial injuries, chronic wounds, pressure ulcers, diabetic foot ulcers, chronic venous ulcers, artery insufficiency ulcers, wounds from aesthetic skin treatments, wounds from ablative laser skin treatments, wounds from chemical peels, wounds from dermabrasion, wounds resulting from adverse drug reactions, wounds resulting from toxic epidermal necrolysis, wounds resulting from Lyell syndrome, wounds resulting from Stevens-Johnson syndrome, and wounds resulting from radiation dermatitis. 
     
     
         68 . A method of treating a wound in a patient comprising topically administering the foam of any one of  claims 52 - 60  to at least a portion of the wound. 
     
     
         69 . The foam of any one of  claims 52 - 60 , for use in a method of treating a wound. 
     
     
         70 . The method or foam for use of  claim 69 , wherein the wound is selected from the group consisting of burns, surgical skin lesions, superficial injuries, chronic wounds, pressure ulcers, diabetic foot ulcers, chronic venous ulcers, artery insufficiency ulcers, wounds from aesthetic skin treatments, wounds from ablative laser skin treatments, wounds from chemical peels, wounds from dermabrasion, wounds resulting from adverse drug reactions, wounds resulting from toxic epidermal necrolysis, wounds resulting from Lyell syndrome, wounds resulting from Stevens-Johnson syndrome, and wounds resulting from radiation dermatitis. 
     
     
         71 . A method of treating epidermolysis bullosa in a patient in need thereof comprising topically administering to an area of epidermolysis bullosa of the patient the oleogel of any one of  claims 13 - 31 . 
     
     
         72 . The oleogel of any one of  claims 13 - 31 , for use in a method of treating epidermolysis bullosa. 
     
     
         73 . A method of treating epidermolysis bullosa in a patient in need thereof comprising topically administering to an area of epidermolysis bullosa of the patient the emulsion of any one of  claims 43 - 51 . 
     
     
         74 . The emulsion of any one of  claims 43 - 51 , for use in a method of treating epidermolysis bullosa. 
     
     
         75 . A method of treating epidermolysis bullosa in a patient in need thereof comprising topically administering to an area of epidermolysis bullosa of the patient the foam of any one of  claims 52 - 60 . 
     
     
         76 . The foam of any one of  claims 52 - 60 , for use in a method of treating epidermolysis bullosa.